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An Optoelectronic Attenuator for the High-Speed Control of Microwave Integrated Circuits.
Final rept. Nov 90-Dec 93,
ARMY RESEARCH LAB ADELPHI MD
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An optoelectronic attenuator suitable for the optical control of microwave integrated circuits is presented. High-speed photoconductive switches are embedded in planar microwave transmission lines, and semiconductor laser diodes LDs are used to control the microwave signal level on these high-speed lines. With a silicon coplanar waveguide-photoconductive switch SiCPW-PCS, up to 45 dB of microwave attenuation has been achieved with a fiber-pigtailed laser diode having 144 mW of optical power. Measurements made using a vector network analyzer show that the attenuator performance can be explained by a classical plasma absorption argument, whereby the microwave signal is attenuated by the optically induced solid-state plasma. Edge-coupled Fabry-Perot aluminum-gallium-arsenidegallium-arsenide AlGaAsGaAs semiconductor LDs, as well as both silicon and gallium-arsenide GaAs CPW-PCSs, were developed for the optoelectronic attenuator. When conventional gain-switching techniques are used, LD peak Output powers greater than 1 W have been demonstrated, and when an optical Q-switching scheme is used, 6 W of peak power has been achieved in tens of picoseconds. jg
APPROVED FOR PUBLIC RELEASE